Ink for ball-point pen and ball-point pen

ABSTRACT

In a ballpoint pen which is formed to have an ink-consumption value per unit area of 0.64 to 1.6 mg/cm 2 , the surface tension of the ink for the ball point pen is adjusted to a range of 16 to 32 mN/m so that blotting, line splitting and the like hardly occur, that the ink transferred onto the paper surface is ready to be dried and that fluctuation in the density and width of the written lines are less likely to occur due to a storage environment and to a writing condition.

TECHNICAL FIELD

The present invention relates to ink for a ballpoint pen which is calledmedium viscosity ink, neutral ink, gel ink, aqueous gel ink or the like,and to a ballpoint pen using the ink for a ballpoint pen, morespecifically the present invention relates to ink for a ballpoint penwhich consumes much ink, that is, a ballpoint pen for writing thick andbold letters and a ballpoint pen using the ink for a ballpoint pen.

BACKGROUND ART

Various types of ballpoint pen have been proposed conventionally.

For example, there is provided a ballpoint pen filled with ink usingwater or an aqueous medium as a solvent and dye or pigment as acolorant. Hereinafter the ink is referred to as “aqueous ink” and theballpoint pen as an “aqueous ballpoint pen.”

The aqueous ballpoint pen shows so low viscosity that it mayadvantageously write smoothly at low writing-pressure. On the otherhand, however, it is likely to occur that, since the pen is weak tovibration or impact, the ink leaks from the point of pen-tip(hereinafter referred to as “direct flow”) and that the stability of theink-flow rate decreases (hereinafter referred to as “fluctuating”) bythe air involved from the point of the pen-tip. Further, the aqueousballpoint pen also has a defect that lines written therewith tend to beblurred.

Meanwhile, there is also provided a ballpoint pen filled with ink usingan organic medium as a solvent and dye or pigment as a colorant.Hereinafter the ink is referred to as “oil-based ink” and the ballpointpen as an “oil-based ballpoint pen.”

Since the oil-based ballpoint pen uses highly viscous ink, it is freefrom above-mentioned defects as seen in the aqueous ballpoint pen.However, it has a defect that high writing pressure is needed forwriting, resulting in a heavy writing feeling. Further, it also has adefect that it is likely to make the pen-tip and the paper surface dirtywith ink blots (hereinafter referred to as “blotting”).

There has recently been provided a ballpoint pen filled with ink usingwater or a water-soluble medium as a solvent, dye or pigment as acolorant and, further, a pseudoplasticizing so that the ink may havepseudoplasticity. Hereinafter the of ink is referred to as “aqueous gelink” and the ballpoint pen as an “aqueous-gel ballpoint pen.”

Here, pseudoplasticity is a property showing non-flowability in a staticstate and also showing flowability when a shearing force is applied.

The aqueous gel ink shows non-flowability in an ink reservoir as well asthe oil-based ink while it shows flowability like aqueous ink near thepoint of the pen-tip where a shearing force is applied to the ink due tothe rotation of the ball.

Accordingly, the aqueous-gel ballpoint pen has both the advantage of anaqueous ballpoint pen and that of an oil-based ballpoint pen. That is,the aqueous-gel ballpoint pen has advantages that it can write smoothlyat a low writing pressure, that the lines written there with are hard toblur and that the blotting is less likely to occur.

Actually, however, the production of the aqueous-gel ballpoint pen isnot so easy.

For example, a pen-tip containing a ball with a diameter of 0.5 mm and apen-tip containing a ball with a diameter of 0.7 mm are different in theclearance between the ball and a holder as well as in the shearing forceapplied to the ink caused by rotation of the ball.

Therefore, if aqueous gel ink suitable for one of these two types ofpen-tips is used for the other, the direct flow and fluctuating willoccur or the blotting will occur.

Accordingly, the viscosity of the aqueous gel ink is adjusted inaccordance with the pen-tip to be used.

Further, an aqueous-gel ballpoint pen with which relatively thick andbold letters (hereinafter referred to as an “aqueous-gel bold ballpointpen”) can be written is desired recently.

The aqueous-gel bold ballpoint pen uses a ball with a diameter of 0.9 mmor more so as to be adapted for writing bold letters.

Further, the aqueous-gel bold ballpoint pen is formed to have arelatively large clearance between the ball and the holder since, onlyby enlarging the diameter of the ball, the written line, which can bewider, appears pale in color.

Moreover, the aqueous-gel bold ballpoint pen needs so much ink to besupplied to the pen-tip as to account for the amount according to widerlines due to the larger diameter of the ball and the amount according tothe increase of the flow rate due to the larger clearance between theball and the holder.

Specifically, ink should be supplied to the pen-tip so that theink-consumption value per unit area may fall within a range on the orderof 0.64 to 1.6 mg/cm².

This ink consumption corresponds to as much as 1.5 to 3 times that of aconventional aqueous-gel ballpoint pen.

Here, the ink-consumption value per unit area means a value of theink-consumption value per unit length which is divided by the linewidth.

For example, the ink-consumption value per unit length of an aqueous-gelbold ballpoint pen is preferably on the order of 300 to 750 mg/100 m.When the ink-consumption value per unit length is 300 mg/100 m or less,written lines appear pale in color. On the other hand, when theink-consumption value per unit length is 750 mg/100 m or more, the inktransferred onto the paper surface will be harder to dry.

The line width by the ball with a diameter of 1.0 mm, though it may varydue to the quality of paper, is on the order of 0.47 mm when written onthe writing test paper in compliance with ISO standard 14145-1.

Accordingly, the ink-consumption value per unit area of an aqueous-gelbold ballpoint pen is on the order of 0.64 to 1.6 mg/cm².

Actually, however, the preparation of the ink for an aqueous-gel boldballpoint pen is very difficult.

For example, when ink suitable for a pen-tip with a ball with a diameterof 0.5 mm is used for a pen-tip with a ball with a diameter of 1.0 mm,the blotting and a phenomenon that a written line splits into plurallines (hereinafter referred to as “line splitting”) is likely to occurdue to the larger clearance between the ball and the holder becomes andto the less shearing force applied to the ink caused by rotation of theball.

In addition, the amount of ink flow from the point of the pen-tipincreases in the aqueous-gel bold ballpoint pen, and consequently theink transferred onto the paper surface becomes harder to dry.

Further, since the amount of ink flow from the point of the pen-tipbecomes unstable in such an aqueous-gel bold ballpoint pen due to astorage environment and to a writing condition, there occurs a widevariation in the density and width of the written lines.

DISCLOSURE OF THE INVENTION

Accordingly, the object of the present invention is to provide ink for aballpoint pen to be used in an aqueous-gel bold ballpoint pen asdescribed above which is unlikely to cause blotting or line splitting,which is excellent in quick drying property when transferred onto thepaper surface and which is unlikely to cause fluctuation in the densityand width of the written lines due to a storage environment and to awriting condition.

Further, the object of the present invention is to provide anaqueous-gel bold ballpoint pen as described above which is unlikely tocause blotting or line splitting, which is excellent in quick dryingproperty when transferred onto the paper surface and which is unlikelyto cause fluctuation in the density and width of the written lines dueto a storage environment and to a writing condition.

The present inventors have made intensive studies to achieve theabove-described objects and found that a ballpoint pen formed to have anink-consumption value per unit area of 0.64 to 1.6 mg/cm², when thesurface tension of the aqueous gel ink to be used is adjusted to a rangeof 16 to 32 mN/m, is unlikely to cause blotting and line splitting. Theyalso found that the ink transferred onto the paper surface therewith isexcellent in quick drying property and that the density and the width ofthe lines written therewith are unlikely to vary due to a storageenvironment and to a writing condition, and thus completed the followinginventions.

Namely, the present invention is characterized in that ink for aballpoint pen to be used in a ballpoint pen formed to have anink-consumption value per unit area of 0.64 to 1.6 mg/cm² has surfacetension adjusted to a range of 16 to 32 mN/m.

Here, the term “ink-consumption value per unit area” means a valueobtained by dividing an “ink-consumption value per unit length” by the“line width.”

The term “ink-consumption value per unit length” means anink-consumption value per unit length according to ISO standards.

The ink-consumption value per unit length can be measured by using awriting test machine in compliance with ISO standard 14145-1 underspecified conditions (e.g., at a writing speed of 4.5 m/min, a writingangle of 60° and a writing load of 100 g).

The term “line width” means a width of a line written on the paper.

The line width may vary depending on the quality of paper but it is onthe order of 0.47 mm when the line is written on the writing test paperin compliance with ISO standard 14145-1 by a ball with a diameter of 1.0mm.

As described above, since the ink-consumption value per unit length ofan aqueous-gel bold ballpoint pen is preferably on the order of 300 to750 mg/100 m, the ink-consumption value per unit area of an aqueous-gelbold ballpoint pen with a ball with a diameter of 1.0 mm, for instance,is on the order of 0.64 to 1.6 mg/cm².

Here, the term “surface tension” means the surface tension in accordancewith ISO standard.

The surface tension can be measured by a vertical plane method using asurface tension meter manufactured by, for example, Kyowa InterfaceScience Co., Ltd.

And when the surface tension of the ink for a ballpoint pen to be usedin a ballpoint pen formed to have a consumption value per unit area of0.64 to 1.6 mg/cm², that is, in a ballpoint pen for writing thick andbold letters is adjusted to a range of 16 to 32 mN/m, writing with theballpoint pen, blotting and line splitting is unlikely to occur, the inktransferred onto the paper surface is easier to dry, and the fluctuationin the density and width of the written lines is unlikely to occur dueto a storage environment and to a writing conditions.

If the surface tension of the ink for a ballpoint pen is 16 mN/m orless, direct flow is likely to occur and pigment used there in is likelyto coagulate and sediment. On the other hand, if the surface tension ofthe ink for a ballpoint pen is 32 mN/m or more, blotting and linesplitting are likely to occur, the ink transferred onto the papersurface is hard to dry, and further the ink-flow rate becomes unstabledue to a storage environment and to a writing conditions, thereby makingfluctuation in the density and width of the written lines more likely tooccur.

Moreover, the ink for a ballpoint pen, in addition to theabove-mentioned character, is characterized in that it includes fluorinesurfactant in an amount of 0.01 to 1.5 wt %.

Here, the possible examples of the “fluorine surfactant” areperfluoroalkylethylene oxide adducts (e.g., SURFLON S-145 (trade name,Asahi Glass Co., Ltd.) and UNIDYNE DS-401 (trade name, Daikin IndustriesLtd.)); perfluoroalkyltrimethylammonium salts (e.g., MEGAFAC F-150(trade name, Dainippon Ink and Chemicals, Inc.));perfluoroalkylcarboxylate salts (e.g., SURFLON S-111 (trade name, AsahiGlass Co., Ltd.)); copolymers of polyoxyalkylene glycol monoesteracrylate and N-perfluorooctylsulfonyl-N-propylaminoethyl acrylate (e.g.,EF-352 (trade name, Tochem Products)); fluorinated alkyl esters (e.g.,Fluorad FC-430 (trade name, Sumitomo 3M Ltd.)); perfluoroalkylsulfonatesalts; oligomers containing perfluoroalkyl group and hydrophilic group;urethanes containing perfluoroalkyl group and hydrophilic group;perfluoroalkyl phosphates; perfluoroalkyl betaines; perfluoroalkylamineoxides; perfluoroalkylammonium salts; perfluoroalkyl alkoxylates;perfluoroalkyl polyoxyethyleneethanol; etc.

Addition of the fluorine surfactant in an amount of 0.01 to 1.5 wt %facilitates the surface tension of ink for a ballpoint pen to beadjusted to a range of 16 to 32 mN/m. Moreover, when such an adjustedink for a ballpoint pen is used in a ballpoint pen, it is possible tomake blotting and line splitting less likely to occur, to make the inktransferred onto the paper surface easier to dry, and further to makethe fluctuation in the density and width of the written lines lesslikely to occur due to a storage environment and to a writing condition.

If the content of fluorine surfactant is 0.01 wt % or less, surfacetension of the ink shows 32 mN/m or more, blotting and line splittingare likely to occur, the ink transferred onto the paper surface is hardto dry, and further the ink-flow rate becomes unstable due to a storageenvironment and to a writing condition, thereby causing fluctuation inthe density and width of the written lines more likely to occur. On theother hand, if the content of fluorine surfactant is 1.5 wt % or more,surface tension of the ink shows 16 mN/m or less, direct flow is likelyto occur and the pigment used therein likely to coagulate and sediment.

Further, the present invention is characterized in that a ballpoint penformed to have an ink-consumption value per unit area of 0.64 to 1.6mg/cm²is filled with ink for a ballpoint pen which has surface tensionadjusted to a range of 16 to 32 mN/m.

When a ballpoint pen formed to have a consumption value per unit area of0.64 to 1.6 mg/cm², that is, a ballpoint pen for writing thick and boldletters is filled with ink whose surface tension is adjusted to a rangeof 16 to 32 mN/m, blotting and line splitting are less likely to occur,the ink transferred onto the paper surface is easier to dry, and furtherthe fluctuation in the density and width of the written lines is lesslikely to occur due to a storage environment and to a writing conditionwhen such a ballpoint pen is used for writing.

If the surface tension of the ink for a ballpoint pen is 16 mN/m orless, direct flow is likely to occur and pigment used therein is likelyto coagulate and sediment. On the other hand, if the surface tension ofthe ink for a ballpoint pen is 32 mN/m or more, blotting and linesplitting are likely to occur, the ink transferred onto the papersurface is hard to dry, and further the ink-flow rate becomes unstabledue to a storage environment and to a writing conditions, thereby makingfluctuation in the density and width of the written lines more likely tooccur.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the ink for a ballpoint pen and the ballpoint pen usingthe ink for a ballpoint pen according to the present invention will behereinafter described.

Ink for a Ballpoint Pen

The ink for a ballpoint pen according to an embodiment of the presentinvention is to be used in a ballpoint pen which is formed to have anink-consumption value per unit area of 0.64 to 1.6 mg/cm² and thesurface tension thereof is adjusted to a range of 16 to 32 mN/m.

The ink for a ballpoint pen according to the embodiment also containscolorant, water-soluble medium, fluorine surfactant, humectant,lubricant, preservative, rust preventive, pH-adjusting agent, thickener,water, etc.

Colorant

Any kind of dye or pigment which has been used for ink for a ballpointpen and which can be dissolved or dispersed in water can be used ascolorant.

Specifically, for example, following acid dyes can be used as colorant:C.I. Acid Black 1, 2, 24, 26, 31, 52, 107, 109, 110, 119 and 154; C.I.Acid Yellow 7, 17, 19, 23, 25, 29, 38, 42, 49, 61, 72, 78, 110, 141,127, 135 and 142; C.I. Acid Red 8, 9, 14, 18, 26, 27, 35, 37, 51, 52,57, 82, 87, 92, 94, 111, 129, 131, 138, 186, 249, 254, 265, and 276;C.I. Acid Violet 15 and 17; C.I. Acid Blue 1, 7, 9, 15, 22, 23, 25, 40,41, 43, 62, 78, 83, 90, 93, 103, 112, 113 and 158; and C.I. Acid Green3, 9, 16, 25 and 27.

For example, following basic dyes can also be used as colorant: C.I.Basic Yellow 1, 2 and 21; C.I. Basic Orange 2, 14 and 32; C.I. Basic Red1, 2, 9 and 14; C.I. Basic Violet 1, 3 and 7; C.I. Basic Brown 12; andC.I. Basic Black 2 and 8.

In addition, for example, following direct dyes can also be used ascolorant: C.I. Direct Black 17, 19, 22, 32, 38, 51 and 71; C.I. DirectYellow 4, 26, 44 and 50; C.I. Direct Red 1, 4, 23, 31, 37, 39, 75, 80,81, 83, 225, 226 and 227; and C.I. Direct Blue 1, 15, 71, 86, 106 and119.

In addition, for example, following inorganic pigments can also be usedas colorant: titanium oxide, carbon black, red ironoxide, chromiumoxide,black ironoxide, cobalt blue, alumina white, yellow iron oxide,viridian, zinc sulfide, lithopone, cadmium yellow, vermilion, cadmiumred, chrome yellow, molybdate orange, zinc chromate, strontium chromate,white carbon, clay, talc, ultramarine, precipitated barium sulfate,baryte powder, calcium carbonate, white lead, Prussian blue, manganeseviolet, aluminum powder, stainless steel powder, nickel powder, copperpowder, zinc powder and bronze powder.

In addition, for example, following organic pigments can also be used ascolorant: azo lake, insoluble azo pigments, chelate azo pigments,phthalocyanine pigments, perylene and perinone pigments, anthraquinonepigments, quinacridone pigments, dye lakes, nitropigments andnitrosopigments, more specifically, organic pigments such as phthalocyanineblue (C.I. 74160), phthalocyanine green (C.I. 74260), Hansa yellow 3G(C.I. 11670), disazo yellow GR (C.I. 21100), Permanent red 4R (C.I.12335), Brilliant carmine 6B (C.I. 15850) and quinacridone red (C.I.46500).

Each of these dyes and pigments may be used alone or two or more of themmay be used in combination.

The content of the colorant is preferably on the order of 0.1 to 40 wt %to the total amount of the ink for a ballpoint pen. If the content ofthe colorant is 0.1 wt % or less, written lines look pale in color. Onthe other hand, if the content of the colorant 40 wt % or more, the inkbecomes unstable during the time course.

Water-soluble Medium

Any kind of polar solvent which can dissolve in water can be used aswater-soluble medium.

Specifically, following polar solvents can be used as water-solublemedium: alkyleneglycols such as ethyleneglycol, diethylene glycol,triethylene glycol, tetraethylene glycol, propylene glycol, dipropyleneglycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol,2,3-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-pentanediol,1,5-pentanediol, 2,5-hexanediol, 3-methyl-1,3-butanediol,2-methylpentane-2,4-diol, 3-methylpentane-1,5-diol, 1,2,3-butanetriol,1,2,4-butanetriol, 3-methylpentane-1,3,5-triol and 1,2,3-hexanetriol;polyalkylene glycols such as polyethylene glycol and polypropyleneglycol; glycerols such as glycerol, diglycerol and triglycerol;loweralkyl ethersofglycols such as ethylene glycol monomethyl ether,ethylene glycol monoethyl ether, diethylene glycol monomethyl ether,diethylene glycol monoethyl ether and diethylene glycol mono-n-butylether; thiodiethanol; N-methyl-2-pyrrolidone;1,3-dimethyl-2-imidazolidinone; and sulfolane.

Each of these polar solvents may be used alone or two or more of themmay be used in combination.

The content of the water-soluble medium is preferably on the order of 1to 40 wt % to the total amount of the ink for a ballpoint pen. If thecontent of the water-soluble medium is 1 wt % or less, writing feelingis deteriorated. On the other hand, if the content of the water-solublemedium is 40 wt % or more, the ink transferred onto the paper surfacebecomes hard to dry.

Fluorine Surfactant

Any kind of surfactant which contains fluorine and can be dissolved ordispersed in water can be used as fluorine surfactant.

Specifically, for example, perfluoroalkylethylene oxide adducts (e.g.,SURFLON S-145 (trade name, Asahi Glass Co., Ltd.) and UNIDYNEDS-401(tradename, Daikin Industries, Ltd.)), perfluoroalkyltrimethylammoniumsalts (e.g., MEGAFAC F-150 (trade name, Dainippon Ink and Chemicals,Inc.)), perfluoroalkylcarboxylate salts (e.g., SURFLON S-111 (tradename, Asahi Glass Co., Ltd.)), copolymers of polyoxyalkylene glycolmonoester acrylate and N-perfluorooctylsulfonyl-N-propylaminoethylacrylate (e.g., EF-352 (trade name, Tochem Products)), fluorinated alkylesters (e.g., Fluorad FC-430 (trade name, Sumitomo 3M Ltd.)),perfluoroalkylsulfonate salts, oligomers containing perfluoroalkyl groupand hydrophilic group, urethanes containing perfluoroalkyl group andhydrophilic group, perfluoroalkyl phosphates, perfluoroalkyl betaines,perfluoroalkylamine oxides, perfluoroalkylammonium salts, perfluoroalkylalkoxylates, perfluoroalkyl polyoxyethyleneethanol, etc. can be used.

Addition of fluorine surfactant in an amount 0.01 to 1.5 wt % to thetotal amount of the ink for a ballpoint pen facilitates the surfacetension of ink for a ballpoint pen to be adjusted to a range of 16 to 32mN/m.

Each of these fluorine surfactants may be used alone or two or more ofthem may be used in combination.

If the content of fluorine surfactant is 0.01 wt % or less, blotting andline splitting are likely to occur, the ink transferred onto the papersurface is hard to dry, and further the ink-flow rate becomes unstabledue to a storage environment and to a writing condition, thereby causingfluctuation in the density and width of the written lines more likely tooccur. On the other hand, if the content of fluorine surfactant is 1.5wt % or more, surface tension of the ink shows 16 mN/m or less, directflow is likely to occur and the pigment used therein likely to coagulateand sediment.

Humectant

Sugars such as reducing sugars comprising maltitol as a major component,reducing sugars comprising sorbitol as a major component, reducingoligosaccharides, reducing maltooligosaccharides, dextrins,maltodextrins, reducing dextrins, reducing maltodextrins,α-cyclodextrin, β-cyclodextrin, maltosylcyclodextrins, hardly digestibledextrins, reducing starch hydrolyzates, xylitol, saccharose, maltitol,reducing saccharified starches and reducing maltose can be used ashumectant.

Specifically, for example, TK-16 and TK-75 (trade name, MatsutaniChemical Industry Co., Ltd.), Diatol N and Diatol K (trade name, San-eiSucrochemical Co., Ltd.), SE 20 and SE 58 (trade name, Nikken ChemicalsCo., Ltd.), PO-300 and PO-20 (trade name, Towa Chemical Industry Co.,Ltd.), etc. can be used as humectant.

Each of these sugars may be used alone or two or more of them may beused in combination.

The content of the humectant is preferably on the order of 0.1 to 10 wt% to the total amount of the ink for a ballpoint pen. If the content ofthe humectant is 0.1 wt % or less, effect of the humectant cannot beexhibited. On the other hand, if the content of the humectant is 10 wt %or more, the ink becomes hard to dry when transferred onto the papersurface.

Lubricant

Fatty acid salts and nonionic surfactants can be used as lubricant.

Specifically, for example, aliphatic acids such as potassium linoleate,potassium oleate and sodium oleate and nonionic surfactants such asglycerine fatty acid esters, polyglycerine fatty acid esters, propyleneglycol fatty acid esters, pentaerythritol fatty acid esters,polyoxyethylene sorbitanfattyacidesters, pentaerythritolfattyacidesters, polyoxyethylene sorbitan fatty acid esters,polyoxyethylene sorbit fattyacidesters, polyoxyethylene glycerinefattyacid esters, polyethylene glycol fatty acid esters, polyoxyethylenealkyl ethers, polyoxyethylene fitosterol, polyoxyethylenepolyoxypropylene alkyl ethers, polyoxyethylene alkylphenyl ethers,polyoxyethylene castor oil, polyoxyethylene lanolin, polyoxyethylenelanolin alcohol, polyoxyethylene alkylamines, polyoxyethylene fatty acidamides and polyoxyethylene alkylphenylformaldehyde condensation productscan be used as lubricant.

Each of these aliphatic acids and nonionic surfactants may be used aloneor two or more of them may be used in combination.

Preservative

For example, sodiumomadine, 1,2-benzoisothiazoline, etc. can be used aspreservative.

Each of them may be used alone or two or more of them may be used incombination.

Rust Preventive

Examples of usable rust preventives include tolyltriazole, benzotriazoleand derivatives thereof, fatty acid derivatives containing phosphorussuch as octyl phosophate and dioctyl thiophosphate, imidazole,benzimidazole and derivatives thereof, 2-mercaptobenzothiazole, octyloxymethanephosphonate, dicyclohexylammonium nitrite, diisopropylammoniumnitrite, propargyl alcohol, dialkyl thiourea, saponins, etc.

Each of these compounds may be used alone or two or more of them may beused in combination.

pH-adjusting Agent

Inorganic alkalis and organic amines can be used as a pH-adjustingagent.

Specific examples of usable pH-adjusting agents include inorganicalkalis such as sodium hydroxide, potassium hydroxide, potassiumphosphate, calcium hydroxide, sodium carbonate, sodium hydrogencarbonate, ammonia, etc. and organic amines such as methylamine,dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine,propylamine, dipropylamine, tripropylamine, butylamine, dibutylamine,tributylamine, isobutylamine, diisobutylamine, 2-butaneamine,N-(1-methylpropyl)-1-propaneamine, N,N-dimethylbutylamine,1,2-dimethylpropylamine, N-ethyl-1,2-dimethylpropylamine, allylamine,diallylamine, triallylamine, N,N-dimethylallylamine,N-methyldiallylamine, 3-pentylamine, N,N-diisopropylethylamine,2-(hydroxymethylamino)ethanol, 2-aminopropanol, 3-aminopropanol,triethanolamine, monoethanolamine, diethanolamine,2-amino-2-methyl-1-propanol, N-isobutyldiethanolamine,3-methoxypropylamine, 3-propyloxypropylamine, 3-isopropyloxypropylamine,3-butoxypropylamine, etc.

Each of these inorganic alkalis and organic amines may be used alone ortwo or more of them may be used in combination.

Thickener

Examples of usable thickeners include gum arabic, tragacanthgum,locustbeangum, guar gum and their derivatives, alginicacid,alginicacidsalts, pectin, carrageenan, gelatin, casein, sodium casein,xanthane gum, rhamsan gum, welan gum, gellan gum, dextran, methylcellulose, ethyl cellulose, hydroxyethyl cellulose, carboxymethylcellulose, hydroxypropyl cellulose, sodium starch glycolate, lanolinderivatives, chitosanderivatives, lactalbumin, polyethylene oxide,polyethylene glycol, polyvinyl alcohol, polyvinyl methyl ether,polyvinylpyrrolidone and derivatives thereof, polyacrylic acid resins,bridging polyacrylic resin, polyurethane resins, alkali metal salts ofacrylic resin, etc.

Specifically, for example, Junron PW-111 (trade name, Nippon Jun-yakuCo., Ltd.), Hiviswako 103 (trade name, Wako Pure Chemical Industries,Co., Ltd.), KELZAN, KELZANAR, K1A96, K1A112, RHEOZAN and K7C233 (tradename, Sansho Co., Ltd.), JAGUAR HP-8, JAGUAR HP-60, RHODOPOL23 andRHODOPOL 50MC (trade name, Rhone Poulenc Japan, Ltd.), Echo Gum GH(trade name, Dainippon Pharmaceutical Co., Ltd.), etc. can be used.

Each of them may be used alone or two or more of them may be used incombination.

Water

Water composes a major part of the ingredients of the ink for aballpoint pen other than the above-mentioned ingredients from colorantto thickener. Distilled water or ion-exchanged water is used in theembodiment.

The water content is preferably on the order of 30 to 80 wt % to thetotal amount of the ink for a ballpoint pen. If the water content is 30wt % or less, the ink-flow rate from the point of the pen-tip decreases.On the other hand, if the water content is 80 wt % or more, the contentsof the other ingredients than the above-mentioned ones are relativelylarge and the ink becomes unstable during the time course.

Other ingredients

In addition to the above-mentioned ingredients, resins such as ammoniumsalts of styrene maleic acid or ammonium salts of styrene acrylic acidmaybe added as dispersant of pigment.

Production Method for Ink for a Ballpoint Pen

Method for producing ink for a ballpoint pen of the embodiment does notdiffere specially from those for producing conventional ink for aballpoint pen.

That is, ink for a ballpoint pen of the embodiment can be produced bymixing and stirring the above-described ingredients.

Ballpoint Pen

Hereinafter, the ballpoint pen according to the present invention willbe described.

The ballpoint pen according to the embodiment is formed to have anink-consumption value per unit area of 0.64 to 1.6 mg/cm² and filledwith ink for a ballpoint pen whose surface tension is adjusted to arange of 16 to 32 mN/m.

More specifically, the ballpoint pen according to the embodimentcomprises a pen-tip and an ink reservoir.

Pen-tip

The pen-tip is provided with a ball and a holder, and the holder holdsthe ball freely rotatably in the distal end of the holder.

The ball is formed of a hard metal and has a diameter of 1.0 mm.

The holder is formed by cutting out a linear material of stainlesssteel. The holder is provided with a ball house, an ink inducing holeand so on.

The ball is placed in the ball house of the pen-tip and then a spun partis formed around the distal end of the holder, thereby holding the ballfreely rotatably in the distal end of the holder.

The clearance between the ball and the holder is so adjusted that theink-consumption value per unit area is about 0.64 to 1.6 mg/cm², thatis, so that thick and bold letters can be written.

The ball may also be formed of hardened steel or ceramic.

The ball diameter is not limited to 1.0 mm and may be, for example, 0.9mm or 1.1 mm provided that the ink-consumption value per unit area isadjusted to a value in the range of about 0.64 to 1.6 mg/cm².

The holder may be formed by cutting out a linear material of a metal,for example, nickel silver or brass, or alternatively, for example, maybe formed by cutting a pipe steel material.

Ink Reservoir

The ink reservoir is formed of a resin tube. The ink reservoir ispositioned and linked to the back end of the above-described pen-tip.And the ink reservoir is filled with the ink for a ballpoint pen asdescribed above.

Production Method for a Ballpoint Pen

Method for producing a ballpoint pen of the embodiment does not differespecially from those for producing conventional ballpoint pens.

That is, a ballpoint pen can be produced by forming a pen-tip asdescribed above, positioning an ink reservoir linking to the back end ofthe pen-tip, filling the ink reservoir with ink for a ballpoint pen, andthen effecting a centrifugal treatment to remove air contained in theink for a ballpoint pen.

Effect

Thus, a ballpoint pen can be provided which is less likely to causeblotting, line splitting or the like and is excellent in quick dryingproperty when ink is transferred onto the paper surface and further lesslikely to cause fluctuation in the density and width of the writtenlines due to a storage environment and to a writing condition byadjusting the surface tension of ink for a ballpoint pen to be used in aballpoint pen which is formed to have an ink-consumption value per unitarea of 0.64 to 1.6 mg/cm² to a range of 16 to 32 mN/m.

In other words, blotting, line splitting and the like can be made lesslikely to occur and quick drying property when ink is transferred ontothe paper surface is improved and further fluctuation in the density andwidth of the written lines can be prevented due to a storage environmentand to a writing condition by filling a ballpoint pen which is formed tohave an ink-consumption value per unit area of 0.64 to 1.6 mg/cm² withink for a ballpoint pen whose surface tension is adjusted to a range of16 to 32 mN/m.

If the surface tension of the ink for a ballpoint pen is 16 mN/m orless, direct flow is likely to occur and the pigment used therein likelyto coagulate and sediment. On the other hand, if the surface tension ofthe ink for a ballpoint pen is 32 mN/m or more, blotting, line splittingand the like tend to occur and the ink transferred onto the papersurface is hard to dry and further the ink-flow rate becomes unstabledue to a storage environment and to a writing condition, thereby causingfluctuation in the density and width of the written lines more likely tooccur.

Addition of fluorine surfactant in an amount of 0.01 to 1.5 wt %facilitates the surface tension of the ink for a ballpoint pen to beadjusted to a range of 16 to 32 mN/m.

Hereinafter, the present invention will be illustrated in more detail byway of examples and comparative examples.

EXAMPLE 1

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: carbon black: 7.0 wt %

Resin: ammonium salts of styrene acrylic acid resin: 2.0 wt %

Water-soluble medium: propylene glycol: 15.0 wt %

Fluorine surfactant: perfluoroalkyl suflonate salt: 1.0 wt %

Humectant: maltitol: 5.0 wt %

Lubricant: phosphate ester: 0.6 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.4 wt %

Thickener: polyacrylic resin: 0.2 wt %

Water: ion-exchanged water: 68.5 wt %

EXAMPLE 2

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: carbon black: 7.0 wt %

Resin: ammonium salts of styrene acrylic acid resin: 2.0 wt %

Water-soluble medium: propylene glycol: 15.0 wt %

Fluorine surfactant: perfluoroalkyl suflonate salt: 0.05 wt %

Humectant: maltitol: 5.0 wt %

Lubricant: phosphate ester: 0.6 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.4 wt %

Thickener: polyacrylic resin: 0.4 wt %

Water: ion-exchanged water: 69.2 wt %

EXAMPLE 3

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: phthalocyanine blue: 7.5 wt %

Resin: ammonium salts of styrene maleic acid resin: 2.2 wt %

Water-soluble medium: glycerine: 15.0 wt %

Fluorine surfactant: fluorinated alkyl ester: 0.5 wt %

Humectant: maltitol: 3.0 wt %

Lubricant: potash soap: 0.5 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.3 wt %

Thickener: polyacrylic resin: 0.3 wt %

Water: ion-exchanged water: 70.4 wt %

EXAMPLE 4

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: phthalocyanine blue: 1.5 wt %

Colorant: titanium oxide: 20.0 wt %

Resin: ammonium salts of styrene maleic acid resin: 2.5 wt %

Water-soluble medium: 4 mol-adduct of propylene oxide to diglycerine:5.0 wt %

Fluorine surfactant: perfluoroalkyl phosphate ester: 1.0 wt %

Humectant: maltitol: 5.0 wt %

Lubricant: potash soap: 0.5 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.3 wt %

Thickener: Arabic gum: 0.4 wt %

Water: ion-exchanged water: 63.5 wt %

EXAMPLE 5

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: phthalocyanine blue: 7.5 wt %

Resin: ammonium salts of styrene maleic acid resin: 2.2 wt %

Water-soluble medium: glycerine: 15.0 wt %

Fluorine surfactant: fluorinated alkyl ester: 0.5 wt %

Humectant: maltitol: 3.0 wt %

Lubricant: potash soap: 1.0 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.3 wt %

Thickener: polyacrylic resin: 0.3 wt %

Water: ion-exchanged water: 69.9 wt %

Comparative Example 1

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: carbon black: 7.0 wt %

Resin: ammonium salts of styrene acrylic acid resin: 2.0 wt %

Water-soluble medium: propylene glycol: 15.0 wt %

Fluorine surfactant: perfluoroalkyl suflonate salt: 1.8 wt %

Humectant: maltitol: 5.0 wt %

Lubricant: phosphate ester: 0.6 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.4 wt %

Thickener: polyacrylic resin: 0.2 wt %

Water: ion-exchanged water: 67.7 wt %

Comparative Example 2

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: carbon black: 7.0 wt %

Resin: ammonium salts of styrene acrylic acid resin: 2.0 wt %

Water-soluble medium: propylene glycol: 15.0 wt %

Fluorine surfactant: none

Humectant: maltitol: 5.0 wt %

Lubricant: phosphate ester: 0.6 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.4 wt %

Thickener: polyacrylic resin: 0.4 wt %

Water: ion-exchanged water: 69.3 wt %

Comparative Example 3

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: phthalocyanine blue: 7.5 wt %

Resin: ammonium salts of styrene maleic acid resin: 2.2 wt %

Water-soluble medium: glycerine: 15.0 wt %

Fluorine surfactant: none

Humectant: maltitol: 3.0 wt %

Lubricant: potash soap: 0.5 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.3 wt %

Thickener: polyacrylic resin: 0.3 wt %

Water: ion-exchanged water: 70.9 wt %

Comparative Example 4

Ink for a ballpoint pen was prepared by blending the followingingredients:

Colorant: phthalocyanine blue: 1.5 wt %

Colorant: titanium oxide: 20.0 wt %

Resin: ammonium salts of styrene maleic acid resin: 2.5 wt %

Water-soluble medium: 4 mol-adduct of propylene oxide to diglycerine:5.0 wt %

Fluorine surfactant: perfluoroalkyl phosphate ester: 0.005 wt %

Humectant: maltitol: 5.0 wt %

Lubricant: potash soap: 0.5 wt %

Preservative: sodium omadine: 0.2 wt %

Rust preventive: saponin: 0.1 wt %

pH-adjusting agent: aminomethylpropanol: 0.3 wt %

Thickener: Arabic gum: 0.4 wt %

Water: ion-exchanged water: 64.5 wt %

Results of Measurement of Surface Tension and Writing Test

Surface tension of the ink for a ballpoint pen of the above-describedexamples 1 to 5 and comparative examples 1 to 4 was measured.

Writing test was also conducted on each of ballpoint pens filled withthe ink of the above-described examples 1 to 5 and comparative examples1 to 4.

The results are shown in the Table 1 below.

The measurement of surface tension was conducted by a vertical planemethod in accordance with the ISO standard using a surface tension metermanufactured by Kyowa Interface Science Company, Ltd.

Writing test was conducted using ballpoint pens with a ball with adiameter of 1.0 mm and formed to have an ink-consumption value per unitarea of 0.64 to 1.6 mg/cm².

The ink-consumption value per unit area was determined by measuring theink-consumption value per unit length using a writing test machine incompliance with ISO standard 14145-1 under conditions at a writing speedof 4.5 m/min, a writing angle of 60° and a writing load of 100 g anddividing the thus measured value by the line width.

Writing test was conducted with a writing test machine in compliancewith ISO standard 14145-1 and by “spiral writing” under the conditionsat a writing speed of 4.5 m/min, a writing angle of 60° and a writingload of 100 g until the ink was used up. The test paper used for thewriting test was compliant with ISO standard 14145-1.

The stability of ink-flow rate, presence or absence of the blotting,presence or absence of the line splitting, quick drying property of thewritten lines and the stability of ink during the time course wereestimated by way of this writing test.

The stability of ink-flow rate was estimated by judging the results ofthe writing test in three levels as “Excellent,” “Good” and “Bad”according to the following criteria:

(i) The example or comparative example in which the ink-flow ratemeasured at every 100 m were constant and in which thin spots orunevenness in thickness until the ink was used up were hardly observedwas estimated as “Excellent;”

(ii) The example or comparative example in which the ink-flow ratemeasured at every 100 m varied to some extent and in which thin spotsand unevenness in thickness until the ink was used up were slightlyobserved was estimated as “Good;” and

(iii) The example or comparative example in which the ink-flow ratesmeasured at every 100 m varied significantly and in which thin spots andunevenness in thickness until the ink was used up were obviouslyobserved was estimated as “Bad.”

Presence or absence of the blotting was estimated by judging the resultsof the writing test in three levels as “Excellent,” “Good” and “Bad”according to the following criteria:

(i) The example or comparative example in which the occurrence ofblotting was hardly observed was estimated as “Excellent;”

(ii) The example or comparative example in which the occurrence ofblotting was slightly observed estimated as “Good;” and

(iii) The example or comparative example in which the occurrence ofblotting was obviously observed was estimated as “Bad.”

Presence or absence of the line splitting was estimated by judging theresults of the writing test in three levels as “Excellent,” “Good” and“Bad” according to the following criteria:

(i) The example or comparative example in which the occurrence of linesplitting was hardly observed was estimated as “Excellent;”

(ii) The example or comparative example in which the occurrence of linesplitting was slightly observed was estimated as “Good;” and

(iii) The example or comparative example in which the occurrence of linesplitting was obviously observed was estimated as “Bad.”

The quick drying property of the written lines was estimated by judgingthe results of the writing test in three levels as “Excellent,” “Good”and “Bad” according to the following criteria:

(i) The example or comparative example in which the written lines gotdried in 30 seconds or less after written was estimated as “Excellent;”

(ii) The example or comparative example in which the written lines gotdried in 30 seconds to one minute after written was estimated as “Good;”and

(iii) The example or comparative example in which the written lines didnot dried in one minute after written was estimated as “Bad.”

The stability of ink with time was estimated by measuring the viscosityof the ink immediately after its production and after it had been storedin a glass bottle in environment at 50° C. for one month and judging theresults in two levels “Excellent” and “Bad” according to the followingcriteria:

(i) The example or comparative example in which viscosity change withtime was hardly observed was estimated as “Excellent;” and

(ii) The example or comparative example in which viscosity change withtime was significantly observed was estimated as “Bad.”

In Table 1, “A” stands for stability of ink-flow rate, “B” for presenceor absence of the blotting, “C” for presence or absence of the linesplitting, “D” for quick drying property of the written lines and “E”for stability with the ink.

TABLE 1 Surface Tension (mN/m) A B C D E Ex. 1 17.8 Excell. Excell.Excell. Excell. Excell. Ex. 2 31.4 Excell. Excell. Excell. Excell.Excell. Ex. 3 25.0 Excell. Excell. Excell. Excell. Excell. Ex. 4 27.3Excell. Good Excell. Excell. Excell. Ex. 5 25.0 Excell. Excell. GoodExcell. Excell. Comp. 15.1 Excell. Excell. Excell. Excell. Bad Ex. 1Comp. 35.8 Bad Bad Good Good Excell. Ex. 2 Comp. 34.3 Bad Good Good GoodExcell. Ex. 3 Comp. 35.2 Bad Bad Good Good Excell. Ex. 4

As indicated above, the ballpoint pens filled with ink of Examples 1 to5 exhibited estimation as “Excellent” or “Good” on each of stability ofink-flow rate, presence or absence of the blotting, presence or absenceof the line splitting, quick drying property of the written lines andstability with time of ink. That is, these ballpoint pens are lesslikely to cause blotting, line splitting and the like and excellent inquick drying property of the ink transferred onto the paper surface andfurther less likely to cause fluctuation in the density and width of thewritten lines due to a storage environment and to a writing condition.

On the other hand, the ballpoint pens filled with ink of ComparativeExamples 1 to 4 exhibited at least one estimation as “Bad” on either oneof stability of ink-flow rate, presence or absence of the blotting,presence or absence of the line splitting, quick drying property of thewritten lines and stability with time of ink. That is, these ballpointpens are likely to cause blotting, line splitting and the like and poorin quick drying property of the ink transferred onto the paper surfaceand further likely to cause fluctuation in the density and width of thewritten lines due to a storage environment and to a writing conditions.

Moreover, experiments for determining the limit values of the surfacetension were conducted and it was confirmed that blotting, linesplitting and the like hardly occur, that the ink transferred onto thepaper surface is ready to be dried and that fluctuation in the densityand width of the written lines are less likely to occur due to a storageenvironment and to a writing condition when the surface tension is atleast in a range of 16 to 32 mN/m.

It was also confirmed that, even if the fluorine surfactant is not addedor other materials are added, blotting, line splitting and the likehardly occur, the ink transferred onto the paper surface is ready to bedried and fluctuation in the density and width of the written lines areless likely to occur due to a storage environment and to a writingcondition as long as the surface tension is adjusted to a range of 16 to32 mN/m.

Therefore, it was confirmed that direct flow is likely to occur and thepigment is likely to coagulate and sediment with the surface tensionbeing 16 mN/m or less, while blotting, line splitting and the like tendto occur and the ink transferred onto the paper surface is hard to dryand fluctuation in the density and width of the written lines tend tooccur depending on storage environment and writing conditions with thesurface tension being 32 mN/m or more.

Further, it was confirmed that addition of fluorine surfactant in anamount of 0.01 to 1.5 wt % facilitates the surface tension of ink for aballpoint pen to be adjusted to a range of 16 to 32 mN/m.

The prevent invention is not limited to the above-described examples.

Industrial Applicability

As described above, according to the present invention, ink for aballpoint pen can be provided which is useful for a ballpoint pen forwriting thick and bold letters, and which is less likely to causeblotting, line splitting and the like, excellent in quick dryingproperty of the ink upon transferred onto the paper surface and furtherless likely to cause fluctuation in the density and width of the writtenlines due to a storage environment and to a writing condition.

Furthermore, according to the present invention, a ballpoint pen forwriting thick and bold letter scan be provided which is less likely tocause blotting, line splitting and the like, excellent in quick dryingproperty of the ink transferred onto the paper surface and further lesslikely to cause fluctuation in the density and width of the writtenlines due to a storage environment and to a writing condition.

What is claimed is:
 1. Ink for a ballpoint pen to be used in anaqueous-gel bold ballpoint pen comprising a ball having a diameter of0.9 mm or more formed to have an ink-consumption value per unit area of0.64 to 1.6 mg/cm²; which includes fluorine surfactant in an amount of0.01 to 1.5 wt %; and whose surface tension is adjusted to a range of 16to 32 mN/m.
 2. An aqueous-gel bold ballpoint pen comprising a ballhaving a diameter of 0.9 mm or more formed to have an ink-consumptionvalue per unit area of 0.64 to 1.6 mg/cm²; which is filled with ink fora ballpoint pen which includes fluorine surfactant in an amount of 0.01to 1.5 wt % and whose surface tension is adjusted to a range of 16 to 32mN/m.